Additional safety measures will be introduced before the 2013 Oxford v Cambridge University Boat Race to avoid a repeat of last year's disruption.
In April, protester Trenton Oldfield swam into the path of the crews causing the race to be halted, before Cambridge won it after it had been restarted.
Oldfield was jailed for six months for causing a public nuisance.
Race director David Searle has appealed for no repeats in this year's event on 31 March, saying: "Please don't do it."
He added: "We've got eight-and-a-half miles of riverbank where somebody could go in so it is very, very difficult to stop someone if they want to do it."
Oldfield, who was released from prison in December, told BBC Radio 5 live he did not regret the incident.
Without specifying what action was being taken, Searle insisted security would be increased for this year's race. "We are taking additional measures this year and we have looked at all of our actions last year," he said.
"We've reviewed them and thought about how we would react slightly differently, not much differently, if it happened this year. We had practised emergency stops and it worked. We got the race restarted eventually and it finished.
"What I would say to anybody thinking of doing that, is that it's unbelievably dangerous.
"You risk getting killed, which would be tragic for them and for the people involved. Nobody wants that to happen. This is just a sporting event."